Regional differences in gully network connectivity based on graph theory: a case study on the Loess Plateau, China

Material exchange frequently occurs in gullies, and thus the relationship between a gully-network structure and sediment transport potential has attracted considerable interest. However, previous researches ignored the difficulty of material transport from sources to sinks, and did not quantify the connectivity of a network structure. In this study, we used a graph model structure to model gully networks of six typical sample areas in the Loess Plateau of China and quantified gully network connectivity using four indexes: average node strength, accessibility from sources to sinks, potential flow, and network structural connectivity index. Results show that: (1) Reflected by different quantitative indexes, the trends of gully network connectivity in different regions are similar. From north to south, the connectivity of a sample area first increases and then decreases. (2) The more mature gullies have stronger network connectivity. Small resistance is conducive to material transport in the gullies. (3) The node connectivity index of the gully network shows a significant aggregation distribution in space, and node connectivity on the main channel is often stronger than that on the branch trench. These results not only deepen the understanding of the process and mechanism of loess gully geomorphic development and evolution but also provide a reference for geomorphic studies.